FAQ

 In addition to developing the corresponding physical and chemical requirements in product technical requirements according to the product characteristics, the administrative counterpart should also simulate the actual clinical use conditions to verify the declared special properties. The verification test should at least consider product design, intended use, use method, service life and other aspects so as to develop the test method suitable for the product under application based on product characteristics. In the process of developing a test protocol, at least the following should be considered:

1. The test procedure should be consistent with actual clinical practice;
2. The selection of test conditions should cover the situations that may be involved in the clinical settings;
3. The sample size should be able to reflect the scientific of test;
4. The number of verification should be more than the number of uses declared for the product;
5. Other relevant guidance documents, etc.

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The device characteristic description on the product structure and design of dental implant should at least include the following:

1. Implant shape, specific nominal values and tolerances of length and diameter (e.g. body diameter and platform diameter);
2. Macroscopic design parameters of threads (e.g. single­thread, double-thread, triple-thread). Geometric parameters of thread unit, include thread shapes (e.g. V-shaped, rectangle, saw tooth, buttress thread, reverse-buttress thread, and square), thread pitch and thread depth;
3. Implant neck characteristics (e.g. bone level, soft tissue level);
4. Contour design of implant apex region (e.g. blunt, sharp, cylindrical, conical) and apex region thread angle (e.g. symmetrical, upper flat and lower taper, upper taper and lower flat);
5. Implant-abutment connection type (e.g. internal hexagon connection, external octagon connection and Morse taper connection);
6. Axial plane characteristics of the implant (e.g. axial anti­rotation groove);
7. Platform switching design (if any);
8. Other structure and design characteristics specific to the product under application.

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The performance studies of PMMA bone cement products should focus on the performance studies of powders and liquids, and the performance studies of the final product after mixing the powders and liquids, including but not limited to the following:

1. Study on the components and ratios of the powder and liquid, the morphology and particle size distribution of the powder components;
2. Molecular weight, such as viscosity-average molecular weight, number-average molecular weight/weight-average molecular weight;
3. Polymer structure, such as graft, linear or copolymerization;
4. Physical properties, such as porosity, shrinkage, water absorption, etc.;
5. The stability of components, such as aging caused by liquid absorption and polymerization, changes in liquid viscosity after being heated, changes (aging) in benzoyl peroxide;
6. Evaluation of monomer residues, such as the amount of monomers precipitated during and after polymerization, the amount of residual monomers after polymerization, and the safety evaluation of monomer residues toxicity;
7. The study of dynamic and static mechanical properties of product considering the applicable site of patients;
8. Study on the polymerization of powder and liquid mixture of PMMA bone cement during the intended use.

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As for implantable medical devices which are degradable and absorbable, if relevant published literature by research institutions is intended to be used as the performance research data on product degradation, the difference between the products or materials in the literature and the product under application should be analyzed to determine its effect on the evaluation result of degradation performance. Generally, a degradation study includes studies of degradation products and degradation period. For a study on degradation period, if the published literature is not related to the product under application, it will have limited value for reference, because the degradation period of products is correlated with the performance parameters (e.g. molecular weight, distribution of molecular weight, crystallinity and etc. of a polymer) and the manufacturing process of the component materials of products. In this case, administrative counterparts are recommended to conduct experimental studies on degradation period of the product under application. For metabolism studies on degradation products, if the degradation products for the devices or raw materials in the literature are the same with those of the product under application, then the research data in literature on metabolism of degradation products can be referred. And the administrative counterpart may submit the related literature and analyze the effects of different implantation sites (if involved) on

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Surface treatment with sand-blasting and acid-etching is one of the methods for surface modification of dental implants and is also an important factor affecting implant osseointegration. The dental implant with sandblasted and acid-etched surface should be subject to a comprehensive study on surface performance, which should at least include the following: clarifying the sand-blasting particles as well as the particle size and particle size distribution of the sand-blasting particles, and providing the basis for setting various parameters (e.g. sand-blasting pressure, time, sand-blasting speed, angle and distance, etc.) during sand-blasting; clarifying the composition of acid etchant and the ratio thereof (volume ratio or mass ratio), and providing the basis for determining the composition ratio of acid etchants, acid­etching time and conditions; providing the high-resolution product surface drawing after surface treatment and indicating the models of relevant test instruments and equipment used; and providing the analysis data of product surface morphology under electron microscope at different scale of magnifications, which should include quantitative and qualitative analysis, such as analysis on the number and distribution of Class I and II cavities.

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The technical review of metallic powder materials for additive manufacturing in dentistry mainly focus on three aspects: the performance requirements of metallic powder for additive manufacturing in dentistry, the process parameter validation of additive manufacturing and the performance of printed test pieces after additive manufacturing and forming. The performance requirements of metallic powder for additive manufacturing in dentistry include but not limited chemical composition (oxygen, hydrogen and impurity elements), sphericity, powder particle size and size distribution, flowability, apparent density, and tap density. For process parameter validation of additive manufacturing, it is necessary to clarify the printing parameters of the printing equipment and printing equipment systems compatible with the product, including but not limited to laser power, spot diameter, scanning interval, powder spreading thickness and scanning speed. In addition, it is necessary to submit the validation and verification report on various parameters and specify the relevant parameters in product technical requirements (PTR) and instructions for use (IFU). The performance requirements for the printed test piece after additive manufacturing and forming include the verification of the mechanical strength of the printed test piece in each direction, which should simulate as far as possible the actual use of the dental restorations in clinical application, with its fat

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 It is recommended to submit the extraction study report for the product under application, clarifying the extraction method and the basis for determining the extraction limit. If the extraction study report of products of the same kind or similar products is submitted as the basis for such determination, it is recommended to select products with similar formulation, e.g., those only with differences in content of color additives. It is not recommended to select products with significant differences with the product under application in formulation. It is also recommended to describe the similarities and differences between the selected products and the product under application and demonstrate that such selected products are representative, which can be discussed from raw material formulation, dry weight of both products, recommended wearing period, etc., and analyze whether the differences affect the results of extraction study. Attention should be given to the rationality of the upper limit of extraction rate.

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 When evaluate the safety of DEHP, suitable extraction solution (e.g. ethanol water) and test method should be adopted to detect the total amount of DEHP extractable in the product by using the tubing set with the highest DEHP content and simulating the most stringent clinical usage conditions (e.g. reference to the method of preparing test solution for chemical performance as specified in YY 0267, a flow rate of 200 mL/min or the maximum blood flow rate declared for the product in clinical use, circulation at 37°C for 5.5 hours). At the same time, the toxicity analysis, safety limit of human blood exposure to DEHP and the corresponding source basis should be provided, and intended population with different body weights should be evaluated respectively concerning their physiological characteristics for the safety of DEHP

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Yes. The mode of connection between dental implant and abutment is among the contents that should be specified in the product structure and components. The modes of implant-abutment connection is mainly classified into external and internal connection types, and can also be classified into internal square connection, external hex connection, external octagon connection, internal hexagon connection and Morse taper connection by geometric shapes. Based on different modes of connection, the administrative counterpart should respectively carry out the relevant studies on the verification of system compatibility such as the taper fit of internal connection of the implant, the fit clearance between the implant and the abutment, the torsional property, the tightening torque and the fatigue limits.

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Yes. The oxygen permeation properties of soft contact lenses include two indexes: oxygen permeability Dk and oxygen transmissibility Dk/t, and the latter is directly related to the thickness of the lens. Therefore, when changing the center thickness of the lens, the manufacturer should consider the effect of the change in thickness on properties of the lens to note whether the change in thickness has led to changed nominal value of the oxygen transmissibility Dk/t. If it is necessary to modify such nominal value, the administrative counterpart should submit corresponding test report as supporting data, as well as the basis for determining such nominal value of oxygen transmissibility Dk/t. Meanwhile, the relevant risk analysis should be conducted and verification data should be provided as needed.

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In the case of joint use of multiple receiving coils in the MRI system, the following issues shall be considered in the registration submission:

1. The combination mode, patient positioning mode and corresponding scanning position of the coil should be described in the overview material;
2. The performance of SNR, uniformity, 2D scanning layer thickness, spatial resolution and ghost should be provided in the research data;
3. The product technical requirements shall include the performance requirements of single coil and the performance requirements of multi coil joint use;

For clinical evaluation, the joint combined coil should be combined with the appropriate scanning position.

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